Pain is the most common medical symptom and is a complex phenomenon, involving physiological, emotional, cognitive, cultural, and other variables. The treatment of pain, particularly chronic pain, seems most effective when multi-disciplinary approaches are adopted, including pharmacological, physical, cognitive and behavioral elements.
In many respects, chronic pain has plague dimensions, e.g., about 20% of the population experience lower back pain each year. Lower back pain is the most common source of disability among people below the age of 45. Another highly common, chronic problem affecting considerable numbers of the general population is headaches.
Pharmacological analgesics commonly used to relieve pain, especially opioids, have significant negative side effects, such as vomiting, constipation, nausea, respiratory depression, and more. Tolerance is another major problem associated with many types of painkillers. In addition, the over-use of medication has the potential to exacerbate pain, rather than relieving it. The over-use of acute care medication is associated with chronicity and pervasive headaches.
In view of the above problems related to pharmacological therapy for chronic pain, other treatments have been adopted, including bio-feedback techniques, behavioral and cognitive psychotherapies, holistic treatments, and more.
The use of Virtual Reality (VR) for the treatment of pain entails the use of technologies, including computers and various multimedia peripherals, to produce a simulated (i.e., virtual) environment that the user perceives as being comparable to real world objects and events. The user employs specially designed transducers to interact with displayed images, to move and manipulate virtual objects, and to perform other actions in a manner that engenders a feeling of actual presence in the simulated environment. This is accomplished by having the simulation adjust to movements of the user's body, so that the resulting sensory cues correspond to what the user would expect were the patient to perform the same movements in the real world. One of the cardinal features of VR is the user's sense of actual presence in, and control over, the simulated environment.
Until recently, the application of VR technology in rehabilitation was severely limited by the lack of inexpensive, easy-to-use VR systems. The development of VR platforms having more user-friendly software launched a wave of potential applications to medicine, in general, and rehabilitation, in particular. VR is being used in training for surgical procedures, in educating patients and medical students, and in the treatment of psychological dysfunctions, including phobias and eating and body image disorders. It is also used in the rehabilitation of cognitive processes, such as visual perception and executive functions and for training in daily living activities. In addition, VR has been used to improve range of motion, strength, endurance, balance and other impairments.
The representation of body schema is anatomically associated with multiple frontal-parietal networks that integrate data from various body regions and from the surrounding space, in order to allow functional motor performance. Recent evidence suggests that body schema representation is plastic in its nature thus allowing a learning process to occur especially via visual feedback. The absorption of newly received information is followed by changes in specific neural networks, thereby producing an updated body schema eventually leading to reduced pain and/or improved motor control.
Jose A. Lozano et at. [1] describe a virtual reality workbench, referred to as the VR-Mirror, that supports stroke patients with upper-limb hemiplegia in generating motor images. Visual cues are used to evoke powerful imaginative responses that draw the patient's attention to the underlying dynamic structure of a movement. This is done following four consecutive steps:                i. The patient performs a specified motor exercise with the healthy limb so as to as to allow the system to acquire the basic dynamic features of the movement using a tracking device;        ii. The system then displays the mirror image of the movement performed by the unimpaired extremity. The observation of the reflected limb provides a direct perceptual cue of the impaired limb, thus supporting the patient in generating a compelling mental image of the movement;        iii. The patient is then instructed to mentally rehearse the exercise depicted by the screen;        iv. The patient is now invited to replicate the displayed movement using the impaired limb by following the mirror image.        
It thus emerges that Lozano et al. [1] simulate healthy movement of an impaired limb in order to stimulate mirror movement by an impaired limb. However, there is no suggestion in [1] to simulate healthy movement of an impaired limb in order to overcome fear-induced pain. Moreover, since Lozano et at. [1] generate simulated movement that is a mirror image of movement of a healthy limb, their approach appears not to be appropriate to those many cases where both of a pair of limbs are impaired or when there is no complementary healthy limb that may be used to generate simulated movement of an impaired limb. Since, as noted above, the most chronic pain for those under the age of 45 is lower back pain for which, of course, no complementary mirror image can be simulated, this appears to be a major drawback of the approach suggested by Lozano et at [1].
Craig D. Murray et al. [2] disclose a system for treating phantom pain due to a missing limb, where a patient wears a head-mounted display (HMD) and a tracker mounted on the counterpart healthy limb. A virtual image is generated showing synthesized movement of the missing limb that mirrors movement of the healthy limb. The virtual image depicts a generic faceless virtual body representation that has limited features and “sees” the world from the same perspective as the patient (i.e., a “first person” view). Substantially the same virtual image is presented for all patients and by definition provides no facial identification with a specific patient.
However, even beyond the versatility of prior art approaches, the present inventors base their approach on evidence suggesting that identification of the patient with the displayed image impacts greatly on the effectiveness of the system due to the increasing sense of presence experienced by the patient. Specifically, there is a psychological component whereby a patient who is able to identify closely with the displayed image is better able to imagine himself following the trajectory of the mirror image: and this represents a marked improvement over known systems.
It would therefore be desirable to increase the sense of identification of the patient to the displayed image in virtual reality systems for the treatment of pain and impairment.
Furthermore, as suggested by accumulated evidence, seeing an image of oneself would activate regions in the brain, known as “mirror neurons”, expected to be involved in learning and regaining motor abilities of impaired organ. Thus the present system differs significantly in clinical rationale and implementation from prior art.